Organic electroluminescence display devices (hereinafter referred to as organic EL display devices) preferably have a display with an active matrix drive system in order to achieve screen brightness uniformity and screen rewrite speed. These displays are comprised of an emission unit comprising organic electroluminescent elements (hereinafter referred to as organic EL elements) in each pixel and a drive unit comprising thin-film transistors (hereinafter referred to as TFT).
The organic EL element comprises in order from above the substrate, a first display electrode, an organic functional layer including a light emitting layer, and a second display electrode.
Furthermore, the TFT normally comprises in order a gate electrode made of a thin metal film formed on a glass substrate, a gate insulation layer that covers the gate electrode, a pair of source/drain electrodes separated from and facing towards the gate insulation layer, and a semiconductor layer which forms a channel between the source and drain electrodes. The semiconductor layer comprises inorganic materials such as a-Si (amorphous silicon) and p-Si (polysilicon) and the like.
Organic EL display devices which use a TFT of this construction are normally manufactured using a thin film forming process which requires high temperature processing and vacuum equipment such as CVD (chemical vapor deposition) or sputtering, in addition to a high precision photolithography process. Therefore the burden of equipment costs and running costs is extremely high.
Therefore research and development into organic thin-film transistors (hereinafter referred to as organic TFT) which use a semiconductor layer made of organic compounds has been performed (see Patent document 1). When manufacturing an organic TFT, the method for forming the organic semiconductor layer generally uses a vacuum vapor deposition method if the organic compound of the semiconductor layer is a low molecular weight material, and uses a printing method if high molecular weight materials are used. However, the merits of using organic materials in the semiconductor layer of the transistor are (1) creating a vacuum condition is not required when manufacturing the semiconductor layer, and (2) the semiconductor layer can be manufactured at low processing temperatures so a resin substrate can be used, and in order to be able to take full advantage of these merits, printing methods have been attempted in order to manufacture organic TFT. One of these manufacturing methods is the inkjet method.
The inkjet method sprays very fine droplets containing organic material that form an organic semiconductor layer from fine nozzles toward the coating subject while controlling with an electric signal, in order to form a thin film with the desired shape. Note, the coating subject has the desired shape and has a preformed water repellent bank with an opening corresponding to the shape of the organic TFT semiconductor layer, and the droplets which are sprayed towards this opening are repelled by this bank and are arranged inside the opening.
Patent Document Japanese Patent Kokai No. 2002-343578